1. Field of the Invention
The invention relates to a method and apparatus for drying or curing rigid cylindrical and flexible belt substrates. More particularly, the invention relates to an efficient method and apparatus that is useful in drying or curing spray-coated photoreceptor substrates (metallic or conductive plastic rigid cylinders, metallic or conductive plastic flexible seamless belts, and the like) and, for that matter, any smooth surface object subject to strict cleanliness standards during manufacture.
2. Description of Related Art
A photoreceptor is a rigid cylinder or flexible belt device used in a xerographic apparatus. The photoreceptor substrate is coated with one or more layers of a photoconductive material, i.e., a material whose electrical conductivity changes upon illumination. In xerographic use, an electrical potential is applied across the photoconductive layer and then exposed to light from an image. The electrical potential of the photoconductive layer decays at the portion irradiated by the light from the image, leaving a distribution of electrostatic charge corresponding to the dark areas of the projected image. The electrostatic latent image is made visible by development with a suitable powder. Better control of the coating quality yields better imaging performance.
The coating of a substrate may be accomplished through an automated four step process, whereby the substrate to be coated is first loaded on a support arm structure (step 1) which then moves the substrate to successive processing stations. The substrate is first moved to the cleaning station (step 2) which includes a cleaning chamber for receiving the support arm bearing the substrate and having decontaminating means for removing contaminates from the substrate; and then on to a coating station (step 3) which includes a coating chamber for receiving the support arm bearing the substrate and having an applicator for applying a coating formulation onto the substrate. Finally, the substrate is moved to a curing station (step 4) which includes a curing chamber for receiving the support arm bearing the coated substrate and has curing means for curing the coating on the substrate. An apparatus and method for processing as described above, is detailed generally in U.S. Pat. No. 5,032,052 to Swain, 5,038,707 to Swain et al. and U.S. Pat. No. 5,079,854 to Hammond et al., which are incorporated herein by reference and referred to for purposes of describing a substrate coating and manufacturing process. In addition, as well known in the art, other suitable methods for coating photoconductive layers can be utilized, such as dip coating, vacuum deposition and the like.
The method and apparatus described herein is preferably adaptable for use with either an airless or air atomized spray coating system. However, in an air atomized spray coating system, an air assisted automatic spray gun using high velocity air to atomize the coating formulation is used to spray the coating onto the substrate. Due to high mass transfer rates intrinsic to the use of atomizing air, this method entails considerable evaporative loss of solvent from the spray droplets and requires the use of slow evaporating solvents to prevent excessive solvent loss before the droplets arrive at the substrate. It is difficult to use this method in a sealed environment, and thus difficult to control the solvent humidity surrounding the substrates prior to, during, or after the coating process. In addition, the air atomized spray method creates a considerable amount of overspray which results in higher material usage.